Disc drives are data storage devices that store digital data in magnetic form on a rotating disc. Modem disc drives comprise one or more storage discs that are coated with a magnetizable medium and mounted on the hub of a spindle motor for rotation at a constant high speed. Information is stored on the discs in a plurality of tracks, typically by an array of transducers (“heads”) mounted to a radial actuator for movement of the heads relative to the discs.
During a write operation data is written onto the disc track, and during a read operation the head senses the data previously written onto the disc track and transfers the information to an external environment. Important to both of these operations is the accurate and efficient positioning of the head relative to the center of the desired track on the disc. Head positioning within a desired track is dependent on head-positioning servo patterns, i.e., a pattern of data bits recorded on the disc surface and used to maintain optimum track spacing and sector timing. Servo patterns or information can be located between the data sectors on each track of a disc (“embedded servo”), or on only one surface of one of the discs within the disc drive (“dedicated servo”). Regardless of whether a manufacturer uses “embedded” or “dedicated” servos, the servo patterns are typically recorded on a target disc during the manufacturing process of the disc drive.
Recent efforts within the disc drive industry have focused on developing cost-effective disc drives capable of storing more data onto existing or smaller-sized discs. One potential way of increasing data storage on a disc surface is to increase the recording density of the magnetizable medium by increasing the track density (i.e., the number of tracks per millimeter). Increased track density requires more closely-spaced, narrow tracks, and therefore requiring enhanced accuracy in the recording of servo-patterns onto the target disc surface. This increased accuracy requires that servo-track recording be accomplished within the increased tolerances, while remaining cost effective.
Servo patterns can be recorded on the magnetizable medium of a target disc by a servo track writer (“STW”), either prior to or during the final assembly of the disc drive. Generally, a STW is manufacturing equipment that controls servowriting activities either directly to the discs, or by controlling the partially-assembled disc drive. In either event, however, the purchase and upkeep of the number of STWs necessary to support production requirements can be an alarming capital investment to a business. Recent improvements have been directed at eliminating the need for the STW by using the disc drive components themselves to write the servo patterns. This is known as self-servowriting.
These and other recent improvements in the art have significantly improved both, often competing, goals of enhanced quality and faster throughput. It is to the furthering of those efforts that the embodiments of the present invention are directed.